Placement of Objects using Particle System

Hi everyone, thanks for any help you might be able to give.

So I have a terrain scene where I have added a couple hundred rocks using a particle system on the ground plane. The particle system is simply duplicating a single rock mesh then randomly scaling and rotating it to give a sort of quarry look.

While the particle system is a great start, I want to be able to remove/alter a few of the individual rocks it generates to help them blend better with the overall scene. They need to be “hand-placed”, so changing the seed doesn’t help.

My first attempt was to “make all duplicates real”, then start moving individual rocks. The problem is, now come render time, the BVH build phase takes forever because there are so many objects, even though the total geometry in the image is the same. When the objects are in the particle system, the render is fast.

Any ideas on how to get the scene to render the individually placed rocks as fast as it does the particle system? Or maybe another workaround I’m not thinking of. Thanks!

My advice would be to keep the particle system as a particle system to get you most of the way there, then scatter some duplicated instances of your main rock model in the specific places you want them (duplicating with Alt-D instead of Shift-D). That should get you the results you want.